Loaded cartridge with frangible projectile



April 22, 1952 C wE lN 2,593,637

LOADED CARTRIDGE WITH FRANGIBLE PROJECTILE Filed Dec. 13, 1949 LEWIS c. WELDIN.

INVENTOR.

BY mgwmw AGENT.

Patented Apr. 22, 1952 LOADED CARTRIDGE 'WITHFRANGIBLE PROJ E GTILE Lewis 0. Weldin, Kenvil, N. "J., assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application December 13, 1949, Serial No. 132,791

6 Claims.

This invention relates to loaded cartridges containing :frangible projectiles and more particularly to loaded cartridges containing frangiblez projectiles which are suitable for use in shooting galleries and other types of gunnery training.

A sizable portion of all .22 caliber ammunition manufactured is fired in shooting galleries; Although great care, is usualy ,takento stop all bullets at the end of the range by employing. a backstop, such as a steel plate, there is always the danger of a projectile finally piercing a backstop after considerable use and of a wild shot missing the backstop altogether. With these hazards in mind, the industry has developed an all-lead projectile that fragments upon striking the backstop. However, when this frangible, alllead projectile is fired, the kinetic energy developed is the same as that of a standard lead bullet and persons ,or objects struck by such projectiles can be seriously injured, even when hit at long range. Furthermore, when such projectiles break up against a backstop, lead dust is formed which, in the close atmosphere of a shooting. gallery, constitutes an ever present danger of lead poisoning of the attendants who are constantly exposed. It is, therefore, apparent that while a lead bullet which will. fragment upon striking a solid object is an advance over a solid projectile, such-a projectile still leaves much to be desired.

An object of the present invention, therefore, is a loaded cartridgecontaining a projectile which is completely free from-lead or its compounds and which will not constitute, any danger of poi- SOIliIlg in the closed atmosphere of a shooting gallery. Another object of the invention is a loaded cartridge containing a projectile which is completely frangible and which is heavy enough .to insure accuracy at the necessary range and to function in an automatic,gun,v but which is, at the same, time, lightenough that damage to targetsor injury to personnel isminimized. Additional objects of the invention will become apparent from the specification and appended claims.

Generally described the. present invention is a loaded cartridge having in combination a casing, a priming assembly, a propellent charge of smokeless powder, and afrangible projectile; said projectile containing from 75-90 of a finely-divided metal filler having a density of from 6 to 9 and from 25-10% of a thermoplastic resinous binder containing from 30-75% of ethyl cellulose. According to the preferred embodiment of the invention, the filler is pulverulent iron. According to one embodiment of the invention, the thermoplastic resinousbinder contains ethyl cellulose, a plasticizer for ethyl cellulose, and a stabilizer. According to a further embodiment of the invention, the thermoplastic binder may contain ethyl cellulose, a plasticizer for ethyl cellulose, a thermoplastic resin which is a solid at ordinary room temperatures, and a stabilizer. In any case, a lubricant such as graphite may be incorporated into the binder, if desired. The use of such a lubricant is, however, unnecessary to the operability of the composition. In forming the frangible projectile for use in the cartridge of the invention, -90% by weight of the total projectile should be pulverulent filler, while 10-25% of the total projectile should be thermoplastic binder. The thermoplastic binder will, in all cases, contain from 30-75% ethyl cellulose; from 5- 60% plasticizer. From 0.53% of stabilizer for the ethyl cellulose is preferably added. If desired, the

binder may be made tougher by the addition of up to 60% of a thermoplastic resin which is a solid at room temperature.

To be operable inthe invention, the ethyl cellu lose used must have a high enough viscosity to have the necessary binding power and yet must have a low enough viscosity to be plasticized without inordinate difliculty. Projectiles made with ethyl cellulose having a viscosity of below 50 cps. were found to exhibit unsatisfactorily low physicalstrength while ethyl cellulose having a viscosity of above 500 cps; was found too diificult to plasticize. Ethyl cellulose having an ethoxyl content of from 43-50% has been found satisfactory. Ethyl cellulose having, an ethoxyl content below 43% cannot. be satisfactorily-plasticized whileethyl-cellulose having an ethoxyl content ,of above 50% does not exhibit the necessary thermoplasticity. It is preferred to employ an ethyl cellulose having a viscosity of from -250 cps. and an ethoxyl content of from 47.549%.

The plasticizer employed may be any of the commonly used plasticizers for ethyl cellulose such as plain or bodied castor oi1-;mineral oil;. the glycerol ester of hydrogenated rosin; alkyl-sub- 3 stituted phthalates such as methyl, ethyl, or diamyl phthalate; phosphates such as trlcresyl phosphate; glycerol propionate; methyl phthalyl ethyl glycolate; and the like.

If a thermoplastic resin is employed in the binder as a toughener in accordance with the invention, the resin must be characterized by a melting point high enough to prevent the binder from becoming tacky at any temperature to which the finished cartridge will normally be exposed. It has been found that the thermoplastic resins which are solid at room temperatures are operable when incorporated in the binder with ethyl cellulose in proportions up to 60%. Of the many operable resins in this class, those which are both highly satisfactory, easily obtainable, and cheap are preferred. Examples of the preferred resins include Vinsol (substantially petroleum hydrocarbon-insoluble pine wood resin), Valite (resinous residue derived from cane sugar bagasse), the coumarone resins having a melting point of above room temperature, and ester gum.

Conventional materials which are employed as plate and allowed to cool and harden. The hard mass was then ground in a coffee mill-type grinder and screened through a U. S. S. 20-mesh screen.

Bullets were made from the above molding powder as follows: 10.5 grains of the powder which was at room temperature was compressed by a force of 6000 pounds into a cylinder 0.18 inch in diameter and 1''; inch long. The cylinder was heated to about 160 F. and then inserted into a two-piece steel bullet mold and forced into the correct shape by a force of about 3000 pounds. The resulting projectiles were loaded into standard .22 caliber short rimfire components using as a propellant a commercial .22 short powder containing 39% nitroglycerin, 60% nitrocellulose, and 1% centralite. These cartridges were fired in comparison with a commercially available .22 short gallery cartridge having a projectile which was all lead but which was designed to fragment upon striking a solid object. The following results were obtained from firing 5 cartridges of each type:

1 Bullets fired through paper target. All shots lay in a circle of the diameter stated.

stabilizers for cellulosic materials are operable as stabilizers in the binder of the cartridge of the invention. Such materials include diphenylamine, the centralites, and the like.

In the drawing is shown a part-sectional, partelevational View of a rimfire, .22 cal. gallery cartridge in accordance with the invention.

A frangible projectile I, prepared in accordance with the invention, is seated in the open end of a brass casing 2. The breech end of the casing 2 contains a priming composition 3 disposed within the annular interior of the rim 4. 7

Example 1 A 2000-gram batch of composition for the frangible projectiles in accordance with the present invention was prepared as follows: 33 g. of graphite, 6 g. of diphenylamine, 46 g. of Vinsol (substantially petroleum hydrocarbon-insoluble pine wood resin), 85 g. of the glycerol ester of hydrogenated rosin, and 43 g. of castor oil were heated with stirring to about 375 F. One hundred forty-seven g. of ethyl cellulose having an ethoxyl content of 48.5% and a viscosity of 200 cps. was added slowly with stirring until a smooth consistency was obtained. One thousand six hundred forty g. of oil-free iron fillings (through a U. S. S. -mesh screen) was added and the whole was mixed to insure uniformity. The mix was then poured onto a polished steel 0 ft./sec.

Example 2 Cartridges prepared in accordance with Example 1 and the commercial .22 short gallery cartridges used in Example 1 were fired in comparison at a rolled steel plate 0.027 inch thick placed at varying distances from the muzzle of the gun. The frangible bullet from the cartridges of the invention did not pierce the plate at 30 ft. when fired at a muzzle velocity of 1400 The fragmenting lead bullet from the commercial gallery cartridges, on the other hand, pierced the same steel plate at a distance of ft. although fired at a velocity of 967 ft./sec.

From Examples 1 and 2 it will be seen that the kinetic energy of the bullet of the invention is considerably less than that of the standard lead gallery bullet. Consequently, comparatively less damage results to targets and backstops and the extent of injury in case of accident is greatly reduced. At the same time, there has been no sacrifice in bullet velocity. To the contrary, the results of the tests given show velocities 50% greater than standard to be attained without exceeding the standard pressure level or without reducing the accuracy of the bullet. High velocities are desirable since, due to the redution in flight time of the bullet, the shooters chances of hitting a moving target are increased. Actually, at the ranges used in a shooting gallery, the cartridges of the invention gave greater accuracy than the currently employed gallery cartridges of the art.

Other compositions from which satisfactory projectiles have been formed in accordance with the present invention are given in the following table:

Example?! Examplei Example Exampled Per Per Per Per cent cent cent cent Ethyl cellug. g. g. g.

lose 60 8.5 50 5.5 70 50 5.5 Glycerol ester othydrogenatedrosin--. 20 2.8 35 3.9 30 4.3 50 5.5 Vinsol 1.7 Methyl ester ofhydrogenatedrosin--- 2.8 Diphenylamine 3 0.4 3 0.3 3 0.4 3 0.3 Iron fillings (through 60 mes 600 85.5 800 88.6 600 85.3 800 88.7 Weight 01' .22 short bullet, gr 11.5 12.5 11.5 12.5

l The ethyl cellulose employed in the above examples had a viscosity o! from 150-250 cps. and an ethoxy content of from 47.549%- reghslubstantially petroleum hydrocarbon-insoluble pine wood It will be seen, therefore, that cartridges made in accordance with the present invention are characterized by several distinct advantages over the cartridges presently used in shooting galleries or in other forms of gunnery training. Due to the absence of lead from the bullet, the danger of lead poisonin is completely removed. Furthermore, since the bullet is so much lighter than the currently employed projectiles in the type cartridge described, the kinetic energy developed is substantially less. Consequently, the use of the cartridges of the invention makes it possible to use thinner and less expensive backstops and lighter and less expensive targets. The lower weight of the projectile used in accordance With the invention also diminishes the amount of injury resulting from accidental wild shots even when the frangible bullets are fired at substantially higher velocities than presently employed.

It has been found that projectiles incorporating fillers having a density of below 6 are too light to give the necessary accuracy and too light to function properly in an automatic gun even when incorporated in the projectile in an amount up to 90%. A filler having a density of more than 9 should not be employed since the weight of the projectile becomes too great and the objects of the invention are not attained. Examples of metals which are operable as fillers include antimony, cadmium, copper, iron, nickel, tin, and zinc. Iron, being the cheapest of the operable materials and at the same time being completely satisfactory, is preferred. The metal filler should be finely divided in order that the projectile will frangibilize substantially completely on impact and so that no single large particle of the relatively dense filler will cause substantial injury to the objects struck. For best results, the filler should be divided finely enough to pass through a 30-mesh screen. It is preferred to employ a particle size which will pass through a 60-mesh screen as in the examples.

Although the invention has been specifically described in conjunction with the popular .22 callher ammunition, it is to be understood that cartridges of any caliber are within the scope of the invention. The conventional loading components used by the art in the manufacture of cartridges employing solid projectiles are operable in the present invention.

Since many modifications of the cartridges shown and the bullet compositions specifically illustrated will be possible to those skilled in the art, the invention is to be limited only by the scope of the appended claims.

What I claim and desire to protect by Letters Patent is:

l. A loaded cartridge having in combination a casing, a priming assembly, a propellent charge of smokeless powder, and a frangible projectile, said projectile containing from '75 to 90% of a finely-divided metal filler having a density of from 6 to 9, and from 25 to 10% of a thermoplastic resinous binder containing from 30 to of ethyl cellulose; said ethyl cellulose having a viscosity of between 50 and 500 centipoises and an ethoxyl content of between 43 and 50 2. A loaded cartridge having in combination a casing, a priming assembly, a propellent charge of smokeless powder, and a frangible projectile, said projectile containing from 75 to of finely-divided iron, and from 25 to 10% of a thermoplastic resinous binder containing from 30 to 75% of ethyl cellulose; said ethyl cellulose having a viscosity of between 50 and 250 centipoises and an ethoxyl content of between 43 and 50%.

3. A loaded cartridge according to claim 2 in which the thermoplastic binder comprises from 30 to 75% of ethyl cellulose, from 5 to 60% of a plasticizer for ethyl cellulose, and from 0.5 to 3% of a stabilizer.

4. A loaded cartridge according to claim 2 in which the thermoplastic binder comprises from 30 to 75% of ethyl cellulose, from 5 to 60% of the glycerol ester of hydrogenated rosin, and from 0.5 to 3% of diphenylamine.

5. A loaded cartridge according to claim 2 in which the thermoplastic binder comprises from 30 to 75% of ethyl cellulose, from 5 to 60% of a plasticizer for ethyl cellulose, from 5 to 60% of thermoplastic resin which is a solid at room temperature and from 0.5 to 3% of a, stabilizer.

6. A loaded cartridge according to claim 2 in which the thermoplastic binder comprises from 30 to 75% of ethyl cellulose, from 5 to 60% of castor oil, from 5 to 60% of substantially petroleum hydrocarbon-insoluble pine wood resin, and from 0.5 to 3% of diphenylamine.

LEWIS C. WELDIN.

REFERENCES CITED The following references are of record in the file of this patent: 

1. A LOADED CARTRIDGE HAVING IN COMBINATION A CASING, A PRIMING ASSEMBLY, A PROPELLENT CHARGE OF SMOKELESS POWDER, AND A FRANGIBLE PROJECTILE, SAID PROJECTILE CONTAINING FROM 75 TO 90% OF A FINELY DIVIDED METAL FILLER HAVING A DENSITY OF FROM 6 TO 9, AND FROM 25 TO 10% OF A THERMOPLASTIC RESINOUS BINDER CONTAINING FROM 30 TO 75% OF ETHYL CELLULOSE; AND ETHYL CELLULOSE HAVING A VISCOSITY OF BETWEEN 50 AND 500 CENTIPOISES AND AN ETHOXYL CONTENT OF BETWEEN 43 AND 50%. 